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nickarcade, you would need to go to their site and scroll down, looking for 'Contact us'. Specify the model of the unit, and ask if optical out supports more than 2 channels.
If they are using the current SPDIF consumer standard, or professional standard (can have both), then it should support 15+ channel LPCM (PCM).
HDMI and SPDIF still use an HDA bus (unless its USB SPDIF), which is limited to ~37 Mbits/s. The most you can do I think is 32 channels 24 bit 48k, based on HDMI 2+.
If it comes with its own EDID programmer, then its likely they opted for programmable SPDIF, so I would contact them, use my posts as notes.
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YodaSkate, that feature is app controlled, without the app, I think you simply just set 7.1 and rear blue becomes side, not sure though for me blue defaults to line in.